Methods are known for characterizing the distribution of bone mineral density in people's skeletons. Such characterization can be particularly useful for diagnosing a person's osteoporosis risk.
For this purpose, X-ray images are used of the person's skeleton, which X-rays are taken by projecting X-rays at different energy levels from an X-ray source, such as an X-ray tube, onto the person and then detecting, for each of the energy levels, the extent to which the X-rays are attenuated by that person's tissues.
Analyzing the differential attenuation between tissues makes it possible to visualize the distribution per unit area, or “areal” distribution, of bone mineral density in a plane onto which the person's skeleton is projected.
A drawback of that method, which is known under the name of “Dual X-ray absorptiometry”, is that when the X-ray apparatus requires time between generating two energy levels, during which time the person must remain completely still, since otherwise differential analysis cannot be undertaken between the two images obtained at two energy levels.
Another problem of that method is that it requires X-ray operators to have a high level of training, and it also requires specific installations for generating X-rays at different energy levels.